151
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Thaler JP, Yi CX, Schur EA, Guyenet SJ, Hwang BH, Dietrich MO, Zhao X, Sarruf DA, Izgur V, Maravilla KR, Nguyen HT, Fischer JD, Matsen ME, Wisse BE, Morton GJ, Horvath TL, Baskin DG, Tschöp MH, Schwartz MW. Obesity is associated with hypothalamic injury in rodents and humans. J Clin Invest 2011; 122:153-62. [PMID: 22201683 DOI: 10.1172/jci59660] [Citation(s) in RCA: 1278] [Impact Index Per Article: 98.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 11/02/2011] [Indexed: 01/21/2023] Open
Abstract
Rodent models of obesity induced by consuming high-fat diet (HFD) are characterized by inflammation both in peripheral tissues and in hypothalamic areas critical for energy homeostasis. Here we report that unlike inflammation in peripheral tissues, which develops as a consequence of obesity, hypothalamic inflammatory signaling was evident in both rats and mice within 1 to 3 days of HFD onset, prior to substantial weight gain. Furthermore, both reactive gliosis and markers suggestive of neuron injury were evident in the hypothalamic arcuate nucleus of rats and mice within the first week of HFD feeding. Although these responses temporarily subsided, suggesting that neuroprotective mechanisms may initially limit the damage, with continued HFD feeding, inflammation and gliosis returned permanently to the mediobasal hypothalamus. Consistent with these data in rodents, we found evidence of increased gliosis in the mediobasal hypothalamus of obese humans, as assessed by MRI. These findings collectively suggest that, in both humans and rodent models, obesity is associated with neuronal injury in a brain area crucial for body weight control.
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152
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Abstract
The drive to eat is controlled by neuronal circuits in the hypothalamus that respond to hormones signaling hunger or satiety. In this issue of Cell, Yang et al. (2011) reveal an AMPK-dependent synaptic pathway that sustains excitatory stimulation of the NPY/AgRP neurons that promote feeding behavior until satiety signals kick in.
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153
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Diano S, Liu ZW, Jeong JK, Dietrich MO, Ruan HB, Kim E, Suyama S, Kelly K, Gyengesi E, Arbiser JL, Belsham DD, Sarruf DA, Schwartz MW, Bennett AM, Shanabrough M, Mobbs CV, Yang X, Gao XB, Horvath TL. Peroxisome proliferation-associated control of reactive oxygen species sets melanocortin tone and feeding in diet-induced obesity. Nat Med 2011; 17:1121-7. [PMID: 21873987 DOI: 10.1038/nm.2421] [Citation(s) in RCA: 214] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 06/15/2011] [Indexed: 01/07/2023]
Abstract
Previous studies have proposed roles for hypothalamic reactive oxygen species (ROS) in the modulation of circuit activity of the melanocortin system. Here we show that suppression of ROS diminishes pro-opiomelanocortin (POMC) cell activation and promotes the activity of neuropeptide Y (NPY)- and agouti-related peptide (AgRP)-co-producing (NPY/AgRP) neurons and feeding, whereas ROS-activates POMC neurons and reduces feeding. The levels of ROS in POMC neurons were positively correlated with those of leptin in lean and ob/ob mice, a relationship that was diminished in diet-induced obese (DIO) mice. High-fat feeding resulted in proliferation of peroxisomes and elevated peroxisome proliferator-activated receptor γ (PPAR-γ) mRNA levels within the hypothalamus. The proliferation of peroxisomes in POMC neurons induced by the PPAR-γ agonist rosiglitazone decreased ROS levels and increased food intake in lean mice on high-fat diet. Conversely, the suppression of peroxisome proliferation by the PPAR antagonist GW9662 increased ROS concentrations and c-fos expression in POMC neurons. Also, it reversed high-fat feeding-triggered elevated NPY/AgRP and low POMC neuronal firing, and resulted in decreased feeding of DIO mice. Finally, central administration of ROS alone increased c-fos and phosphorylated signal transducer and activator of transcription 3 (pStat3) expression in POMC neurons and reduced feeding of DIO mice. These observations unmask a previously unknown hypothalamic cellular process associated with peroxisomes and ROS in the central regulation of energy metabolism in states of leptin resistance.
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154
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Mineur YS, Abizaid A, Rao Y, Salas R, DiLeone RJ, Gündisch D, Diano S, De Biasi M, Horvath TL, Gao XB, Picciotto MR. Nicotine decreases food intake through activation of POMC neurons. Science 2011; 332:1330-2. [PMID: 21659607 DOI: 10.1126/science.1201889] [Citation(s) in RCA: 285] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Smoking decreases appetite, and smokers often report that they smoke to control their weight. Understanding the neurobiological mechanisms underlying the anorexic effects of smoking would facilitate the development of novel treatments to help with smoking cessation and to prevent or treat obesity. By using a combination of pharmacological, molecular genetic, electrophysiological, and feeding studies, we found that activation of hypothalamic α3β4 nicotinic acetylcholine receptors leads to activation of pro-opiomelanocortin (POMC) neurons. POMC neurons and subsequent activation of melanocortin 4 receptors were critical for nicotinic-induced decreases in food intake in mice. This study demonstrates that nicotine decreases food intake and body weight by influencing the hypothalamic melanocortin system and identifies critical molecular and synaptic mechanisms involved in nicotine-induced decreases in appetite.
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155
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Abizaid A, Mineur YS, Roth RH, Elsworth JD, Sleeman MW, Picciotto MR, Horvath TL. Reduced locomotor responses to cocaine in ghrelin-deficient mice. Neuroscience 2011; 192:500-6. [PMID: 21699961 DOI: 10.1016/j.neuroscience.2011.06.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 05/31/2011] [Accepted: 06/01/2011] [Indexed: 01/10/2023]
Abstract
Ghrelin, an orexigenic hormone produced by the stomach, increases food intake and enhances the locomotor and rewarding effects of cocaine. Consistent with these behavioral effects, ghrelin increases dopamine cell activity in the mesolimbic system resulting in elevated levels of dopamine release and turnover in target regions such as the ventral striatum. In the current study, we examined the psychostimulant effects of acute and daily cocaine in mice with targeted deletion of the ghrelin gene (ghrelin knockout; KO) and that of their wild-type (WT) littermates. We hypothesized that ghrelin-KO mice would be hyporesponsive to the effects of cocaine as reflected in attenuated locomotor activity following both acute and chronic injections, and that this would be correlated with striatal dopamine and dopamine metabolite concentrations. Results show that the locomotor stimulating effect of cocaine (10 mg/kg) was decreased in ghrelin-KO mice as compared with their WT littermates. In addition, repeated daily injection of cocaine resulted in gradual increases in locomotor activity in WT mice, an effect that was attenuated in ghrelin-KO mice. These behavioral effects were correlated with changes in dopamine utilization in the striatum of WT mice that were not seen in ghrelin-KO mice unless these were pretreated with ghrelin. These data suggest that ghrelin is important for normal function of the mesolimbic dopaminergic system, potentially modulating both dopamine release and reuptake.
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156
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Klöckener T, Hess S, Belgardt BF, Paeger L, Verhagen LAW, Husch A, Sohn JW, Hampel B, Dhillon H, Zigman JM, Lowell BB, Williams KW, Elmquist JK, Horvath TL, Kloppenburg P, Brüning JC. High-fat feeding promotes obesity via insulin receptor/PI3K-dependent inhibition of SF-1 VMH neurons. Nat Neurosci 2011; 14:911-8. [PMID: 21642975 PMCID: PMC3371271 DOI: 10.1038/nn.2847] [Citation(s) in RCA: 184] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 04/28/2011] [Indexed: 01/16/2023]
Abstract
SF-1-expressing neurons of the ventromedial hypothalamus (VMH) control energy homeostasis, but the role of insulin action in these cells remains undefined. We show that insulin activates PI3-kinase (PI3k) signaling in SF-1 neurons and reduces firing frequency in these cells via activation of KATP-channels. These effects are abrogated in mice with insulin receptor (IR) deficiency restricted to SF-1 neurons (SF-1ΔIR-mice). While body weight and glucose homeostasis remain unaltered in SF-1ΔIR-mice under normal chow diet, they exhibit protection from diet-induced leptin resistance, weight gain, adiposity and impaired glucose tolerance. High-fat feeding activates PI3k signaling in SF-1 neurons of control mice, and this response is attenuated in the VMH of SF-1ΔIR-mice. Mimicking diet-induced overactivation of PI3k signaling by disruption of the PIP3-phosphatase PTEN leads to increased body weight and hyperphagia under normal chow diet. Collectively, our experiments reveal a critical role for HFD-induced, insulin-dependent PI3k activation in VMH neurons to control energy homeostasis.
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157
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Martin JR, Lieber SB, McGrath J, Shanabrough M, Horvath TL, Taylor HS. Maternal ghrelin deficiency compromises reproduction in female progeny through altered uterine developmental programming. Endocrinology 2011; 152:2060-6. [PMID: 21325042 PMCID: PMC3075930 DOI: 10.1210/en.2010-1485] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ghrelin has a well-known role in the regulation of appetite, satiety, energy metabolism, and reproduction; however ghrelin has not been implicated in reproductive tract development. We examined the effect of ghrelin deficiency on the developmental programming of female fertility. We observed that female wild-type mice born of ghrelin heterozygote dams (i.e. exposed in utero to ghrelin deficiency) had diminished fertility and produced smaller litters. We demonstrate that exposure to in utero ghrelin deficiency led to altered developmental programming of the reproductive tract. The number of ovarian follicles, corpora lutea, and embryos produced were identical in both exposed and unexposed mice. However wild-type embryos transferred to uteri of mice exposed to in utero ghrelin deficiency had a 60% reduction in the rate of embryo implantation compared with those transferred to wild-type unexposed uteri. We identified significant alterations in the uterine expression of four genes critical for implantation and a defect in uterine endometrial proliferation. Taken together, these results demonstrate that the mechanism of subfertility was abnormal endometrial function. In utero exposure to decreased levels of ghrelin led to defects in developmental programming of the uterus and subsequent subfertility in wild-type offspring.
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158
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Wiedmer P, Strasser F, Horvath TL, Blum D, Dimarchi R, Lutz T, Schürmann A, Joost HG, Tschöp MH, Tong J. Ghrelin-induced hypothermia: a physiological basis but no clinical risk. Physiol Behav 2011; 105:43-51. [PMID: 21513721 DOI: 10.1016/j.physbeh.2011.03.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 03/22/2011] [Accepted: 03/28/2011] [Indexed: 10/18/2022]
Abstract
Ghrelin increases food intake and decreases energy expenditure, promoting a positive energy balance. We observed a single case of serious hypothermia during sustained ghrelin treatment in a male subject, suggesting that ghrelin may play a role in the regulation of body temperature. We therefore investigated the effect of ghrelin treatment on body temperature in rodents and humans under controlled conditions. Intriguingly, we could demonstrate ghrelin binding in axon terminals of the medial preoptic area of the hypothalamus located in the vicinity of cold-sensitive neurons. This localization of ghrelin receptors provides a potential anatomical basis for the regulation of body temperature by ghrelin. However, our follow-up studies also indicated that neither a chronic i.c.v. application of ghrelin in rats, nor a single s.c. injection under cold exposure in mice resulted in a relevant decrease in body core temperature. In addition, a four-hour intravenous ghrelin infusion did not decrease body surface temperature in healthy humans. We concluded that while there is a theoretical molecular basis for ghrelin to modify body temperature in mammals, its magnitude is irrelevant under physiologic circumstances. Hypothermia is not likely to represent a serious risk associated with this agent and pathway.
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159
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Gao XB, Horvath TL. An arousing discovery on catalepsy: orexin regulates vestibular motor functions. Neuron 2011; 69:588-90. [PMID: 21338870 DOI: 10.1016/j.neuron.2011.02.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A study by Zhang et al. in this issue of Neuron reveals a novel mechanism of control of vestibular motor functions by the orexin (hypocretin) system in the perifornical/LH area through the lateral vestibular nucleus in the brainstem. This knowledge provides new insights into the understanding of brain circuitry that controls motor functions and diseases/conditions related to impairments in this circuitry.
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160
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Ravussin Y, Gutman R, Diano S, Shanabrough M, Borok E, Sarman B, Lehmann A, LeDuc CA, Rosenbaum M, Horvath TL, Leibel RL. Effects of chronic weight perturbation on energy homeostasis and brain structure in mice. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1352-62. [PMID: 21411766 DOI: 10.1152/ajpregu.00429.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Maintenance of reduced body weight in lean and obese human subjects results in the persistent decrease in energy expenditure below what can be accounted for by changes in body mass and composition. Genetic and developmental factors may determine a central nervous system (CNS)-mediated minimum threshold of somatic energy stores below which behavioral and metabolic compensations for weight loss are invoked. A critical question is whether this threshold can be altered by environmental influences and by what mechanisms such alterations might be achieved. We examined the bioenergetic, behavioral, and CNS structural responses to weight reduction of diet-induced obese (DIO) and never-obese (CON) C57BL/6J male mice. We found that weight-reduced (WR) DIO-WR and CON-WR animals showed reductions in energy expenditure, adjusted for body mass and composition, comparable (-10-15%) to those seen in human subjects. The proportion of excitatory synapses on arcuate nucleus proopiomelanocortin neurons was decreased by ∼50% in both DIO-WR and CON-WR mice. These data suggest that prolonged maintenance of an elevated body weight (fat) alters energy homeostatic systems to defend a higher level of body fat. The synaptic changes could provide a neural substrate for the disproportionate decline in energy expenditure in weight-reduced individuals. This response to chronic weight elevation may also occur in humans. The mouse model described here could help to identify the molecular/cellular mechanisms underlying both the defense mechanisms against sustained weight loss and the upward resetting of those mechanisms following sustained weight gain.
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161
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Horvath TL, Erion DM, Elsworth JD, Roth RH, Shulman GI, Andrews ZB. GPA protects the nigrostriatal dopamine system by enhancing mitochondrial function. Neurobiol Dis 2011; 43:152-62. [PMID: 21406233 DOI: 10.1016/j.nbd.2011.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 03/01/2011] [Accepted: 03/06/2011] [Indexed: 11/24/2022] Open
Abstract
Guanidinopropionic acid (GPA) increases AMPK activity, mitochondrial function and biogenesis in muscle and improves physiological function, for example during aging. Mitochondrial dysfunction is a major contributor to the pathogenesis of Parkinson's disease. Here we tested whether GPA prevents neurodegeneration of the nigrostriatal dopamine system in MPTP-treated mice. Mice were fed a diet of 1% GPA or normal chow for 4 weeks and then treated with either MPTP or saline. Indices of nigrostriatal function were examined by HPLC, immunohistochemistry, stereology, electron microscopy and mitochondrial respiration. MPTP intoxication decreased TH neurons in the SNpc of normal chow-fed mice; however GPA-fed mice remarkably exhibited no loss of TH neurons in the SNpc. MPTP caused a decrease in striatal dopamine of both normal chow- and GPA-fed mice, although this effect was significantly attenuated in GPA-fed mice. GPA-fed mice showed increased AMPK activity, mitochondrial respiration and mitochondrial number in nigrostriatal TH neurons, suggesting that the neuroprotective effects of GPA involved AMPK-dependent increases in mitochondrial function and biogenesis. MPTP treatment produced a decrease in mitochondrial number and volume in normal chow-fed mice but not GPA-fed mice. Our results show the neuroprotective properties of GPA in a mouse model of Parkinson's disease are partially mediated by AMPK and mitochondrial function. Mitochondrial dysfunction is a common problem in neurodegeneration and thus GPA may slow disease progression in other models of neurodegeneration.
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162
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Gerashchenko D, Horvath TL, Xie X(S. Direct inhibition of hypocretin/orexin neurons in the lateral hypothalamus by nociceptin/orphanin FQ blocks stress-induced analgesia in rats. Neuropharmacology 2011; 60:543-9. [PMID: 21195099 PMCID: PMC3031765 DOI: 10.1016/j.neuropharm.2010.12.026] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 02/03/2023]
Abstract
We recently demonstrated that hypocretin/orexin (Hcrt) and nociceptin/orphanin FQ (N/OFQ) systems coordinately regulate nociception in a mouse model of stress-induced analgesia (SIA). However, the site of N/OFQ action on modulation of SIA was elusive, since N/OFQ was administered via intracerebroventricular (i.c.v.) injection acting on widely distributed N/OFQ receptors (NOP) in the brain. In the present study, we tested the hypothesis that N/OFQ modulates the SIA directly via the inhibition of the Hcrt neurons in the lateral hypothalamus. Using both fluorescent and electron microscopy, we found that N/OFQ-containing neurons are located in the lateral hypothalamus and the N/OFQ-containing fibers make direct contacts with the Hcrt neurons. Paw thermal nociceptive test revealed that the immobilization restraint of the rat increased the thermal pain threshold by 20.5 ± 7.6%. Bilateral microinjection of N/OFQ (9 μg/side) into the rat perifornical area of the lateral hypothalamus, the brain area in which the Hcrt neurons are exclusively located, abolished the SIA. Activity of Hcrt neurons in the same animals was assessed using Fos immunohistochemistry. Percentage of Fos(+)/Hcrt neurons was lower in rats injected with N/OFQ than rats injected with saline, with the difference between groups stronger in the Hcrt neurons located medially to the fornix than in Hcrt neurons located laterally to the fornix. These results suggest that N/OFQ modulation of SIA is mediated by direct inhibition of Hcrt neuronal activity in the perifornical area. The uncovered peptidergic interaction circuitry may have broad implication in coordinated modulation by Hcrt and N/OFQ on other stress adaptive responses.
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163
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Procaccini C, De Rosa V, Galgani M, Abanni L, Calì G, Porcellini A, Carbone F, Fontana S, Horvath TL, La Cava A, Matarese G. An oscillatory switch in mTOR kinase activity sets regulatory T cell responsiveness. Immunity 2010; 33:929-41. [PMID: 21145759 DOI: 10.1016/j.immuni.2010.11.024] [Citation(s) in RCA: 282] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 07/13/2010] [Accepted: 10/22/2010] [Indexed: 02/07/2023]
Abstract
There is a discrepancy between the in vitro anergic state of CD4(+)CD25(hi)FoxP3(+) regulatory T (Treg) cells and their in vivo proliferative capability. The underlying mechanism of this paradox is unknown. Here we show that the anergic state of Treg cells depends on the elevated activity of the mammalian target of rapamycin (mTOR) pathway induced by leptin: a transient inhibition of mTOR with rapamycin, before T cell receptor (TCR) stimulation, made Treg cells highly proliferative in the absence of exogenous interleukin-2 (IL-2). This was a dynamic and oscillatory phenomenon characterized by an early downregulation of the leptin-mTOR pathway followed by an increase in mTOR activation necessary for Treg cell expansion to occur. These data suggest that energy metabolism, through the leptin-mTOR-axis, sets responsiveness of Treg cells that use this information to control immune tolerance and autoimmunity.
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MESH Headings
- Animals
- CD4 Antigens/biosynthesis
- Cell Proliferation/drug effects
- Cells, Cultured
- Clonal Anergy/drug effects
- Clonal Anergy/genetics
- Disease Progression
- Encephalomyelitis, Autoimmune, Experimental/drug therapy
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/metabolism
- Encephalomyelitis, Autoimmune, Experimental/physiopathology
- Forkhead Transcription Factors/biosynthesis
- Humans
- Interleukin-2/immunology
- Interleukin-2/metabolism
- Interleukin-2 Receptor alpha Subunit/biosynthesis
- Leptin/immunology
- Leptin/metabolism
- Mice
- Mice, Inbred C57BL
- Signal Transduction
- Sirolimus/pharmacology
- Sirolimus/therapeutic use
- T-Lymphocytes, Regulatory/drug effects
- T-Lymphocytes, Regulatory/immunology
- T-Lymphocytes, Regulatory/metabolism
- T-Lymphocytes, Regulatory/pathology
- TOR Serine-Threonine Kinases/antagonists & inhibitors
- TOR Serine-Threonine Kinases/immunology
- TOR Serine-Threonine Kinases/metabolism
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164
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Gyengesi E, Liu ZW, D'Agostino G, Gan G, Horvath TL, Gao XB, Diano S. Corticosterone regulates synaptic input organization of POMC and NPY/AgRP neurons in adult mice. Endocrinology 2010; 151:5395-402. [PMID: 20843996 PMCID: PMC2954711 DOI: 10.1210/en.2010-0681] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Changes in circulating hormones, such as leptin and ghrelin, induce alterations in synaptic input organization and electrophysiological properties of neurons of the arcuate nucleus of the hypothalamus. To assess whether changes in circulating glucocorticoids also alter synaptic arrangement and membrane potential properties, we studied the effect of adrenalectomy (ADX) and corticosterone replacement in mice on the proopiomelanocortin (POMC) and neuropeptide Y (NPY)/agouti-related protein (AgRP) neurons of the hypothalamic arcuate nucleus. ADX reduced the number of symmetric, putative inhibitory synapses onto POMC neurons and the number of asymmetric, putative excitatory synapses onto NPY/AgRP neurons. Corticosterone replacement in ADX mice to levels similar to sham-operated animals restored the number of synapses onto POMC and NPY/AgRP neurons to that seen in sham-operated controls. The alterations in the synaptic arrangement in ADX mice were not due to their decrease in food intake as evidenced by the synaptic analysis of the pair-fed control animals. In line with the altered synaptic input organization, a depolarization of POMC membrane potential and a hyperpolarization of NPY/AgRP membrane potential were observed in ADX mice compared with their sham-operated controls. All of these changes reverted upon corticosterone replacement. These results reveal that the known orexigenic action of corticosteroids is mediated, at least in part, by synaptic changes and altered excitability of the melanocortin system.
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165
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Zheng Q, Zhu J, Shanabrough M, Borok E, Benoit SC, Horvath TL, Clegg DJ, Reizes O. Enhanced anorexigenic signaling in lean obesity resistant syndecan-3 null mice. Neuroscience 2010; 171:1032-40. [PMID: 20923696 DOI: 10.1016/j.neuroscience.2010.09.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 09/22/2010] [Accepted: 09/29/2010] [Indexed: 10/19/2022]
Abstract
Obesity is associated with increased risk of diabetes, cardiovascular disease and several types of cancers. The hypothalamus is a region of the brain critical in the regulation of body weight. One of the critical and best studied hypothalamic circuits is comprised of the melanocortinergic orexigenic agouti-related protein (AgRP) and anorexigenic α-melanocyte stimulating hormone (α-MSH) neurons. These neurons project axons to the same hypothalamic target neurons and balance each other's activity leading to body weight regulation. We previously showed that the brain proteoglycan syndecan-3 regulates feeding behavior and body weight, and syndecan-3 null (SDC-3(-/-)) mice are lean and obesity resistant. Here we show that the melanocortin agonist Melanotan II (MTII) potently suppresses food intake and activates the hypothalamic paraventricular nuclei (PVN) in SDC-3(-/-) mice based on c-fos immunoreactivity. Interestingly, we determined that the AgRP neuropeptide is reduced in the PVN of SDC-3(-/-) mice compared to wild type mice. In contrast, neuropeptide Y, coexpressed in the AgRP neuron, is not differentially expressed nor is the counteracting neuropeptide α-MSH. These findings are unprecedented and indicate that AgRP protein localization can be selectively regulated within the hypothalamus resulting in altered neuropeptide response and tone.
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166
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Sotonyi P, Mezei G, Racz B, Dallman MF, Abizaid A, Horvath TL. Gonadotropin-releasing hormone fibers contact POMC neurons in the hypothalamic arcuate nucleus. Reprod Sci 2010; 17:1024-8. [PMID: 20713970 DOI: 10.1177/1933719110378346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The metabolic state has long been shown to affect reproduction. Peripheral signals and hormones from the reproductive organs are also known to regulate energy metabolism and feeding and energy expenditure. Much attention has been paid to determine the signaling flow from key hypothalamic neuronal populations, including those producing the anorexigenic proopiomelanocortin (POMC) derivate, α-melanocyte stimulating hormone (α-MSH), to the medial preoptic area gonadotropin-releasing hormone (GnRH) neurons, cells that are the drivers of ovulation and reproduction in general. In this study, the authors explored whether a reverse signaling modality may also exist. Specifically, the authors analyzed GnRH efferents in the arcuate nucleus with particular emphasis on their anatomical proximity to arcuate nucleus melanocortin perikarya. Using correlated light and electron microscopy, the authors observed direct apposition between GnRH-containing axon terminals and POMC cell bodies. These data provide the first experimental evidence to suggest that GnRH may have a direct influence on feeding, energy expenditure, and glucose homeostasis, independent of the activity of the gonadal axis.
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167
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Sotonyi P, Qian Gao, Bechmann I, Horvath TL. Estrogen Promotes Parvalbumin Expression in Arcuate Nucleus POMC Neurons. Reprod Sci 2010; 17:1077-80. [DOI: 10.1177/1933719110379651] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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168
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Abstract
Neuropathies are severe complications of diabetes. In this issue of Neuron, Campanucci et al. report that hyperglycemia-induced elevation of reactive oxygen species impairs synaptic transmission of sympathetic neurons leading to diabetes-induced dysautonomias. These observations provide new insights into the etiology of diabetic complications and suggest potential novel therapeutic approaches for neuropathies.
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169
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Matarese G, Procaccini C, De Rosa V, Horvath TL, La Cava A. Regulatory T cells in obesity: the leptin connection. Trends Mol Med 2010; 16:247-56. [PMID: 20493774 DOI: 10.1016/j.molmed.2010.04.002] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Revised: 04/06/2010] [Accepted: 04/08/2010] [Indexed: 01/15/2023]
Abstract
Studies to understand the pathogenesis of obesity have revealed mediators that are responsible for the control of food intake and metabolism at the hypothalamic level. However, molecular insight explaining the link between obesity and low-degree chronic inflammation remains elusive. The adipocyte-derived hormone leptin, and thereby the nutritional status, could control immune self-tolerance by affecting regulatory T (Treg) cell responsiveness and function. Furthermore, resident Treg cells, which are capable of modulating metabolism and glucose homeostasis, are abundant in adipose tissue. Here, we provide an update on recent findings relating Treg cells to obesity and discuss how the intricate network of interactions among leptin, Treg cells and adipose tissue might provide new strategies for therapeutic interventions.
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170
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Andrews ZB, Erion DM, Beiler R, Choi CS, Shulman GI, Horvath TL. Uncoupling protein-2 decreases the lipogenic actions of ghrelin. Endocrinology 2010; 151:2078-86. [PMID: 20189996 PMCID: PMC2869261 DOI: 10.1210/en.2009-0850] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The exact mechanisms through which ghrelin promotes lipogenesis are unknown. Uncoupling protein (UCP)-2 is a mitochondrial protein important in regulating reactive oxygen species; however, recent research shows that it may play an important role fat metabolism. Given that ghrelin increases UCP2 mRNA in white adipose tissue, we examined whether the lipogenic actions of ghrelin are modulated by UCP2 using ucp2(+/+) and ucp2(-/-) mice. Chronic ghrelin treatment either via osmotic minipumps or daily ip injections induced body weight gain in both ucp2(+/+) and ucp2(-/-) mice; however, body weight gain was potentiated in ucp2(-/-) mice. Increased body weight gain was completely due to increased body fat as a result of decreased fat oxidation in ucp2(-/-) mice. Ghrelin treatment of ucp2(-/-) mice resulted in a gene expression profile favoring lipogenesis. In a calorie-restriction model of negative energy balance, ghrelin to ucp2(+/+) mice did not increase body weight; however, ghrelin to ucp2(-/-) mice still induced body weight. These results show that UCP2 plays an important role in fat metabolism by promoting fat oxidation and restricts ghrelin-induced lipogenesis.
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171
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Lin HV, Plum L, Ono H, Gutiérrez-Juárez R, Shanabrough M, Borok E, Horvath TL, Rossetti L, Accili D. Divergent regulation of energy expenditure and hepatic glucose production by insulin receptor in agouti-related protein and POMC neurons. Diabetes 2010; 59:337-46. [PMID: 19933998 PMCID: PMC2809966 DOI: 10.2337/db09-1303] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE The sites of insulin action in the central nervous system that regulate glucose metabolism and energy expenditure are incompletely characterized. We have shown that mice with hypothalamic deficiency (L1) of insulin receptors (InsRs) fail to regulate hepatic glucose production (HGP) in response to insulin. RESEARCH DESIGN AND METHODS To distinguish neurons that mediate insulin's effects on HGP from those that regulate energy homeostasis, we used targeted knock-ins to express InsRs in agouti-related protein (AgRP) or proopiomelanocortin (POMC) neurons of L1 mice. RESULTS Restoration of insulin action in AgRP neurons normalized insulin suppression of HGP. Surprisingly, POMC-specific InsR knock-in increased energy expenditure and locomotor activity, exacerbated insulin resistance and increased HGP, associated with decreased expression of the ATP-sensitive K(+) channel (K(ATP) channel) sulfonylurea receptor 1 subunit, and decreased inhibitory synaptic contacts on POMC neurons. CONCLUSIONS The contrasting phenotypes of InsR knock-ins in POMC and AgRP neurons suggest a branched-pathway model of hypothalamic insulin signaling in which InsR signaling in AgRP neurons decreases HGP, whereas InsR activation in POMC neurons promotes HGP and activates the melanocortinergic energy expenditure program.
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172
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Korosi A, Shanabrough M, McClelland S, Liu ZW, Borok E, Gao XB, Horvath TL, Baram TZ. Early-life experience reduces excitation to stress-responsive hypothalamic neurons and reprograms the expression of corticotropin-releasing hormone. J Neurosci 2010. [PMID: 20071535 DOI: 10.1532/jneurosci.4214-09.2010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Increased sensory input from maternal care attenuates neuroendocrine and behavioral responses to stress long term and results in a lifelong phenotype of resilience to depression and improved cognitive function. Whereas the mechanisms of this clinically important effect remain unclear, the early, persistent suppression of the expression of the stress neurohormone corticotropin-releasing hormone (CRH) in hypothalamic neurons has been implicated as a key aspect of this experience-induced neuroplasticity. Here, we tested whether the innervation of hypothalamic CRH neurons of rat pups that received augmented maternal care was altered in a manner that might promote the suppression of CRH expression and studied the cellular mechanisms underlying this suppression. We found that the number of excitatory synapses and the frequency of miniature excitatory synaptic currents onto CRH neurons were reduced in "care-augmented" rats compared with controls, as were the levels of the glutamate vesicular transporter vGlut2. In contrast, analogous parameters of inhibitory synapses were unchanged. Levels of the transcriptional repressor neuron-restrictive silencer factor (NRSF), which negatively regulates Crh gene transcription, were markedly elevated in care-augmented rats, and chromatin immunoprecipitation demonstrated that this repressor was bound to a cognate element (neuron-restrictive silencing element) on the Crh gene. Whereas the reduced excitatory innervation of CRH-expressing neurons dissipated by adulthood, increased NRSF levels and repression of CRH expression persisted, suggesting that augmented early-life experience reprograms Crh gene expression via mechanisms involving transcriptional repression by NRSF.
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Abstract
Food intake is a major physiological function in animals and must be entrained to the circadian oscillations in food availability. In the last two decades a growing number of reports have shed light on the hormonal, cellular and molecular mechanisms involved in the regulation of food intake. Brain areas located in the hypothalamus have been shown to play a pivotal role in the regulation of energy metabolism, controlling energy balance. In these areas, neuronal plasticity has been reported that is dependent upon key hormones, such as leptin and ghrelin, that are produced by peripheral organs. This review will provide an overview of recent discoveries relevant to understanding these issues.
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174
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Dietrich MO, Horvath TL. The role of mitochondrial uncoupling proteins in lifespan. Pflugers Arch 2009; 459:269-75. [PMID: 19760284 DOI: 10.1007/s00424-009-0729-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Accepted: 08/26/2009] [Indexed: 11/27/2022]
Abstract
The increased longevity in modern societies raised the attention to biological interventions that could promote a healthy aging. Mitochondria are main organelles involved in the production of adenosine triphosphate (ATP), the energetic substrate for cellular biochemical reactions. The production of ATP occurs through the oxidative phosphorylation of intermediate substrates derived from the breakdown of lipids, sugars, and proteins. This process is coupled to production of oxygen reactive species (ROS) that in excess will have a deleterious role in cellular function. The damage promoted by ROS has been emphasized as one of the main processes involved in senescence. In the last decades, the discovery of specialized proteins in the mitochondrial inner membrane that promote the uncoupling of proton flux (named uncoupling proteins-UCPs) from the ATP synthase shed light on possible mechanisms implicated in the buffering of ROS and consequently in the process of aging. UCPs are responsible for a physiological uncoupling that leads to decrease in ROS production inside the mitochondria. Thus, induction of uncoupling through UCPs could decrease the cellular damage that occurs during aging due to excess of ROS. This review will focus on the evidence supporting these mechanisms.
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Leinninger GM, Jo YH, Leshan RL, Louis GW, Yang H, Barrera JG, Wilson H, Opland DM, Faouzi MA, Gong Y, Jones JC, Rhodes CJ, Chua S, Diano S, Horvath TL, Seeley RJ, Becker JB, Münzberg H, Myers MG. Leptin acts via leptin receptor-expressing lateral hypothalamic neurons to modulate the mesolimbic dopamine system and suppress feeding. Cell Metab 2009; 10:89-98. [PMID: 19656487 PMCID: PMC2723060 DOI: 10.1016/j.cmet.2009.06.011] [Citation(s) in RCA: 289] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 05/27/2009] [Accepted: 06/25/2009] [Indexed: 12/24/2022]
Abstract
The lateral hypothalamic area (LHA) acts in concert with the ventral tegmental area (VTA) and other components of the mesolimbic dopamine (DA) system to control motivation, including the incentive to feed. The anorexigenic hormone leptin modulates the mesolimbic DA system, although the mechanisms underlying this control have remained incompletely understood. We show that leptin directly regulates a population of leptin receptor (LepRb)-expressing inhibitory neurons in the LHA and that leptin action via these LHA LepRb neurons decreases feeding and body weight. Furthermore, these LHA LepRb neurons innervate the VTA, and leptin action on these neurons restores VTA expression of the rate-limiting enzyme in DA production along with mesolimbic DA content in leptin-deficient animals. Thus, these findings reveal that LHA LepRb neurons link anorexic leptin action to the mesolimbic DA system.
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